How to battle friends on GH3?

I've looked everywhere and can't see where it actually walks you through how to initiate a battle with another person.
We have our friends' code and I went into the WFC to invite them but we are stuck. It just says pending friends.
Can someone tell me exactly what they and I need to do in order to actually battle each other?
Thanks!

I have noticed that when you have friends added and one of them creates a match and invites you, if you go to your friends list, there will be a guitar like icon next to their name. Highlight their name, click the green button and the option to accept invite is there, amongst others. HTH